Titanium dioxide is the most common white pigment due to its strong ability to backscatter visible light, which is in turn dependent on its refractive index. Substitutes for titanium dioxide have been sought, but the refractive indexes of both the anatase and rutile forms of this oxide are much higher than those of any other white powder, due to structural reasons.
Titanium dioxide pigments are insoluble in coating vehicles in which they are dispersed. The performance properties of such titanium dioxide pigments, including its physical and chemical characteristics, are determined by the particle size of the pigment and the chemical composition of its surface. Titanium dioxide is commercially available in two crystal structures: anatase and rutile. Rutile titanium dioxide pigments are preferred as they scatter light more efficiently and are more stable and durable than anatase pigments. Titanium scatters light strongly due to its high refractive index, that is markedly different from that of most resins or paint components. The decorative and functional abilities of titanium dioxide are due to its scattering power that make it a highly desirable pigment. However, titanium dioxide is known to be an expensive pigment to manufacture. Accordingly, there is a need for a more affordable substitute for titanium dioxide as a pigment. There is also a need for methods for cost effective manufacturing of the aluminum phosphate with hollow particles.